Media signals such as video signals, audio signals, and/or audio-video signals, whether in a digital form or an analog form, may be presented in a context where the authenticity of such media signals is put into dispute. For instance, audio-video signals may be captured that appear to show a supernatural phenomenon, an unidentified flying object, and the like. As another example, audio-video signals may be offered as evidence in a court of law or in other proceedings to prove that what is shown on the video signals actually happened.
With the prominence of editing tools, media signals may be edited to present false information. For instance, a media signal carrying audio may have some portions of the audio removed or additional audio added. As another example, a media signal carrying video may have objects inserted in or removed from one or more video frames and frames may be added or deleted. Such editing may be done at a level of proficiency that makes detecting such alterations from merely viewing the content very difficult if not impossible. Thus, the reliability of media signals is subject to scrutiny because of the possibility of editing.
In a court of law, the chain of custody of the storage medium containing the media signal may have to be shown to achieve some level of confidence that the media signal is authentic. Even where the chain of custody is adequately proven to be acceptable, there may still be doubts as to whether someone within the chain of custody has modified the media signals to suit a particular purpose.
Some attempts have been made to provide embedded information into a media signal to show its authenticity. For example, audio and/or video watermarks may be embedded to alter the audio and/or video content to some degree that is perceivable by the viewer. However, such artifacts within the media signals may compromise the content that is of interest in a given situation, and such watermarks may be reproducible. Furthermore, watermarks may not account for some types of editing that may occur.